The present invention relates to a method of surface evaluation, and more particularly, to a method of surface evaluation which predictively simulates and potentially corrects surface defects of a simulated stamping utilizing a true reflection line methodology and computer graphics technology.
In the manufacture of automobiles, the exterior panels of a vehicle are often shaped by a stamping press. Such a stamping press typically incorporates stamping dies and a hydraulic or mechanical press component. In forming, a sheet metal blank is placed between the dies and then the press component is actuated. The dies close and shape the sheet metal blank into the desired shape.
To determine the required die surface, sheet metal blanks are formed with a die having an initial surface. The formed blanks are then evaluated to determine whether the die has the proper shape. If it does not, then the dies are modified based on draw simulation results.
To analyze the resulting shape, reflection machines are often used to check the surface quality of the formed parts. As shown in FIG. 1, reflection machines incorporate a plurality of light bars 10 spaced from each other. The light bars 10 are positioned a predetermined distance away from the panel 12, which is a formed part to be evaluated. An observer at viewpoint 14 observes light reflected by panel 12 which was generated by light bars 10. These reflections are in the form of lines 16. If lines 16 vary from a standard regular pattern, then panel 12 is distorted to some degree from the required configuration, indicating a flaw in the stamping manufacturing process.
While this method adequately allows an individual to determine the accuracy and quality of a manufactured panel, it requires that the die be constructed before it is tested. If the panel does not meet the surface requirement, the die surface must be modified and sometimes reconstructed. This increases the overall manufacturing cost. Specifically, when a stamping die is being designed and tested, it is common that the die does not have the optimum geometry and characteristics to ensure that a formed part has the right surface quality. As a result, if the observer at view point 14 determines that panel 12 has an improper surface quality, the die must be modified and panel 12 must be scrapped. The present invention was developed in light of these drawbacks.
It is, therefore, an object of the present invention to provide a method for predictively determining surface deviation in a simulated stamping which does not require actually forming parts to determine the surface deviation.
The present invention achieves these and other objective by providing a method for evaluating a surface quality of a desired part having a specific shape which comprises the steps of obtaining a CAD model of the desired part, generating at least one true reflection line on the CAD model. Obtaining a simulated blank mesh using FEA simulation software and processing the blank mesh with a springback simulation software to obtain a finite element analysis (FEA) springback blank. True reflect lines are then generated on the FEA springback blank, and the true reflect lines on the FEA spring back blank are compared with the true reflect lines on the CAD model to determine deviation of the true reflection lines on the springback blank from that of the CAD model.
Additional advantages and features of the present invention will become apparent from the subsequent description and the appended claims taken in conjunction with the accompanying drawings.